Sheet rock screws: fine vs coarse thread?

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wrote:

Drywall tips usually have a cup that stops the bit from advancing and the tip will disengage right away because of the taper. With a square drive the bit is straight and has to run out a lot farther to disengage, even if it does have the cup.
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On Tue, 13 Apr 2010 17:04:10 -0400, "Ed Huntress"

Yep, nails ("blue nails") and a lath hatchet. <G>
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wrote:

Typically, it's coarse thread thread for wood studs, fine thread for metal studs. The fine thread screws also have a sharper point so they are easier to start, *especially* when trying to pierce metal studs.
While you might think that you want coarse threads for more "grab" in the metal studs, in reality you want less space *between* the threads so that the thin metal can't move.
Here are some thoughts on using drywall screws for woodworking...
http://www.woodbin.com/misc/drywall_screws.htm
And we haven't even addressed the different types of heads on drywall screws, from "standard" to bugle to flat.
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And never use drywall screws for staging.
Dave
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On 4/13/2010 2:23 PM DerbyDad03 spake thus:

Thanks for that; excellent article. Pretty much jibes with my own experience with drywall vs. wood screws. I much prefer coarse threads for wood. (Never used fine-thread drywall screws for their original intended purpose of securing to metal framing.)
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    [ ... ]

    When my old workplace (a government R&D lab) let out a contract to re-cover all the 30-year-old linoleum-topped metal desks with new fake wood (particle board with wood-grain print plastic on it), they simply dropped the new top over the existing one (made to be a pretty good fit with sides which overlapped the metal top sides), and used some intersting screws. At first glance, they looked like drywall screws, but examining one showed that instead of having a sharp spiral point, they had a drill bit point, so they would drill through the metal and then thread in -- going into pre-drilled and countersunk holes in the sides of the new top.
    That is now about twenty years ago, so I wonder what the desk tops look like now. :-)
    Enjoy,         DoN.
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Yeah? (Um... they're called "self-drilling sheet metal screws". Any ACE Hardware store will have them) <G>
LLoyd
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On Wed, 14 Apr 2010 06:28:43 -0500, Lloyd E. Sponenburgh wrote:

But sheet metal screws don't look like drywall screws. More likely they were Drill Point Drywall Screws, as shown at top of <http://www.aaronswoodscrews.com/DrywallScrews.htm and one screen down in <http://www.smithfast.com/drywallthreads.html . The latter also shows (near the end, after the Trim Head Drywall Screws section) Auger Point Deck Screws that look somewhat like drywall screws. (With Type-17 point, as mentioned in the link Larry Jaques gave, <http://www.midstatesbolt.com/screwpoints.htm .)
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    Yes -- drill point bugle head blued like other drywall screws I've seen.

    The first SELF-DRILLING in that list (just past "TYPE 25 POINT" is exactly what they were using. And given the application, they made sense. One tool (battery powered drill/driver), one screwdriver bit (Phillips) and the screw which did its own drilling. Not what I would have used to make a pretty job, but something which got the contract done quickly. :-)
    The screws were guided by the pre-drilled holes in the replacement desk tops, and the steel which they had to drill through was probably about 12 Gauge or thicker. (I never tried to measure it, but those were *heavy* GSA steel desks.)
    In case it matters, I'm in here from rec.crafts.metalworking, not from alt.home.repair, so what I regularly work with is likely quite different from what the ahr crowd (who is part of the cross-posting) does.
    Enjoy,         DoN.
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Heh, I'm surprised that some here have asserted that it is the fine thread that's used on metal studs, coarse for wood. Not disputing it, just surprised that this would be so, as it would seem that the greater the ratio of major to minor diameter, the more grab possible on thin sheet metal.
In fact, there's a company that exploits this with some fancy sheet metal screws -- forgot their name, but I have a sample pack from them somewhere...
In re-thinking all this, pilot holes could be used to tailor any material to a coarse thread. Except that, well, altho pilot holes are good, they are also a pita.
I used to buy only fine thread, pretty much out of reflex, but now I find myself much more leaning toward coarse thread, overall. Plus, coarse threads are easier to tap, less chip binding it seems.
My understanding is that fine threads on big bolts is a torque/force consideration, for getting mating stuff really tight.
But, other than that, I think fine threads may be pretty much superfluous for general applications, unless, for example, metal studs really do call for a fine thread screw.
Bottom line is, I think I've convinced myself to dispense with fine thread anything, unless an application specifically benefits from a fine thread. Sure will simplify the organization/storage aspect.
--
EA





> Altho framing screws, which afaik are only for metal stud to metal stud,
> also come in coarse and fine thread, so this may muddy this particular
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wrote:

Just my two cents worth:
I've always thought that the fine threads were for metal studs.
I've used the self-drilling ones in metal studs, but also in one room in my house where the ceiling joists were made of something resembling kryptonite. The normal sharp-pointed screws would just not screw all the way in. The self-drilling ones shot right in.
Also, for what it's worth, coarse threads require fewer turns to screw in, and therefore, go in faster.
Just sayin'
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rangerssuck wrote:

Ah, not so. Well, sometimes, maybe. The fine thread screws are double-threaded, so they go in twice as fast as they would otherwise.
Bob
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Now I gotta go look. But not 'till morning.
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In typed:

No, they are not double-threaded. YOu're thinking of something else. Coarse is just that; a much coarser thread, more diameter than a fine, and fewer turns to drive in but I've never found that to be an issue of any kind.
HTH,
Twayne`
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There are 4 types of screws typically used for drywall..
Coarse Thread from 1inch for pocket door walls to 3 inch for going over old sheetrock/plaster , multiple layers in firewalls ...For use with WOOD studs
Sharp Point fine thread..Same as above except for use in METAL framing..
Self Tapping fine thread , sams as above but for higher gauge steel like in exterior or load bearing steel framed walls..
Laminating Screws...Fat coarse thread 1 1/4 screws for laminating sheetrock on steel framed walls as in stairwells or elevator shafts where sheetrock thickness is an inch or more...
Other than sheetrock I use Torx...Square heads are good as well....
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